This application claims priority under 35 U.S.C. xc2xa7119 to FI 20000240, filed in Finland on Feb. 4, 2000, the entire content of which is hereby incorporated by reference. The present invention relates to a method for reducing dust-related problems in rock drilling, in which method air and liquid mist is supplied into a drilling hole to moisten the dust that comes off the drilling hole, the air and moistened dust exiting from the drilling hole being led to a dust separator for separating the dust from the air by leading the air through at least one filter, dust portions that collect into the dust separator being removed therefrom at suitable intervals.
The invention further relates to an arrangement for reducing dust-related problems in rock drilling, the arrangement comprising means for supplying flushing air and liquid into a drilling hole, suction means for sucking air containing stone dust and exiting from the drilling hole, a dust separator for separating the stone dust from the air, means for removing the accumulated dust from the dust separator and a liquid container for storing the liquid to be used for moistening the dust.
Rock drilling creates stone dust which is harmful and complicates working. Various means are therefore used in an attempt to prevent dust from being produced. One solution is to use water as a flushing means in the drilling to bind the dust and take it out of the hole. In a situation where water for some reason cannot be used, the dust has to be removed from the drilling hole with air. For reasons of occupational safety, among others, in such cases efforts are made to collect the dust so that there would be no stone dust left in the air at the drilling site. A typical solution for dust collection is to arrange a suction nozzle meant for the opening of the drilling hole around the drill rod, a hose being provided from the nozzle to the dust separator where the stone dust is separated from air that is led through filters. Stone dust that accumulates into the filters must be removed therefrom at suitable intervals to prevent the filters from being blocked. When there is no drilling going on, the stone dust is allowed to fall from the dust separator onto the ground for example by applying a compressed air pulse. Typically this takes place for example when the drilling of the hole has been completed.
There are drawbacks also in this solution because when the dust is allowed to fall from the dust separator onto the ground, dust is again created. In an attempt to prevent this, some kind of a dust-binding liquid is supplied together with air into the drilling hole to moisten the dust and to produce material that contains dust particles that stick together and therefore cause less dust. However, in practice this is not sufficient. In principle it would be possible to increase the amount of moistening liquid supplied, but that might block the dust-collecting equipment. Moreover, in a situation where an external water supply is not available, the equipment would have to provided with a large water tank, or water, or some other liquid, would have to be constantly brought to the site to allow this arrangement to be implemented.
It is an object of the present invention to provide a method and arrangement that allow dust to be bound into a more solid state, which in turn allows dust formation in connection with rock drilling to be reduced better than before without large amounts of liquid or large volume tanks being needed for handling the liquid. The method of the invention includes, when dust is to be removed, supplying liquid in a mist-like form or as small droplets substantially only in connection with the dust removal to the dust separator""s lower portion below the filters so that the dust portion falling out of the lower end of the dust separator is sufficiently moist. The arrangement of the invention includes means for supplying liquid into the lower portion of the dust separator for moistening the dust that has accumulated into the dust separator when the dust is being removed from the dust separator.
During the emptying of the dust separator, liquid is supplied into its lower portion in the form of mist or extremely small droplets so that the dust falling from the dust separator onto the ground becomes moist and thereby the dust exiting from the dust separator is not dry and does not spread into the environment. Preferably that the liquid supplied into the lower portion of the dust separator during the emptying contains water and a biologically rapidly degradable material that acts in a glue-like manner and/or reduces the surface tension of water, such as a lignin-based material, tall oil, etc.
An advantage of the invention is that by supplying a dust-binding liquid or some other solution into the dust separator only at the time the separator is to be emptied, dust formation can be prevented exactly at the emptying phase and therefore a relatively small amount of liquid is needed for binding the dust. Consequently, a device which for practical reasons requires a fairly small container can carry out its drilling function even for a fairly long time without dust-related problems being caused. The fact that the dust has already been partly moistened with the liquid supplied together with the flushing air further reduces the amount of liquid needed in the dust separator.